The cosmic microwave background. Scoured for gravitational waves and signs of collisions with other universes. NASA / WMAP Science Team/wikimediaPosted on 09/30/2015 9:03:31 AM PDT by SeekAndFind
The existence of parallel universes may seem like something cooked up by science fiction writers, with little relevance to modern theoretical physics. But the idea that we live in a 'multiverse' made up of an infinite number of parallel universes has long been considered a scientific possibility - although it is still a matter of vigorous debate among physicists. The race is now on to find a way to test the theory, including searching the sky for signs of collisions with other universes.
It is important to keep in mind that the multiverse view is not actually a theory, it is rather a consequence of our current understanding of theoretical physics. This distinction is crucial. We have not waved our hands and said: "Let there be a multiverse". Instead the idea that the Universe is perhaps one of infinitely many is derived from current theories like quantum mechanics and string theory.
You may have heard the thought experiment of Schrödinger’s cat, a spooky animal who lives in a closed box. The act of opening the box allows us to follow one of the possible future histories of our cat, including one in which it is both dead and alive. The reason this seems so impossible is simply because our human intuition is not familiar with it.
But it is entirely possible according to the strange rules of quantum mechanics. The reason that this can happen is that the space of possibilities in quantum mechanics is huge. Mathematically, a quantum mechanical state is a sum (or superposition) of all possible states. In the case of the Schrödinger’s cat, the cat is the superposition of 'dead' and 'alive' states.
But how do we interpret this to make any practical sense at all? One popular way is to think of all these possibilities as book-keeping devices so that the only 'objectively true' cat state is the one we observe. However, one can just as well choose to accept that all these possibilities are true, and that they exist in different universes of a multiverse.
String theory is one of our most, if not the most promising, avenue to be able to unify quantum mechanics and gravity. This is notoriously hard because gravitational force is so difficult to describe on small scales like those of atoms and subatomic particles - which is the science of quantum mechanics. But string theory, which states that all fundamental particles are made up of one-dimensional strings, can describe all known forces of nature at once: gravity, electromagnetism and the nuclear forces.
However, for string theory to work mathematically, it requires at least ten physical dimensions. Since we can only observe four dimensions: height, width, depth (all spatial) and time (temporal), the extra dimensions of string theory must therefore be hidden somehow if it is to be correct. To be able to use the theory to explain the physical phenomena we see, these extra dimensions have to be 'compactified' by being curled up in such a way that they are too small to be seen. Perhaps for each point in our large four dimensions, there exists six extra indistinguishable directions?
A problem, or some would say, a feature, of string theory is that there are many ways of doing this compactification –10500 possibilities is one number usually touted about. Each of these compactifications will result in a universe with different physical laws - such as different masses of electrons and different constants of gravity. However there are also vigorous objections to the methodology of compactification, so the issue is not quite settled.
But given this, the obvious question is: which of these landscape of possibilities do we live in? String theory itself does not provide a mechanism to predict that, which makes it useless as we can’t test it. But fortunately, an idea from our study of early universe cosmology has turned this bug into a feature.
During the very early Universe, just after the Big Bang, the Universe underwent a period of accelerated expansion called inflation. Inflation was invoked originally to explain why the current observational Universe is almost uniform in temperature. However, the theory also predicted a spectrum of temperature fluctuations around this equilibrium which was later confirmed by several spacecraft such as Cosmic Background Explorer, Wilkinson Microwave Anisotropy Probe and the PLANCK spacecraft.
While the exact details of the theory are still being hotly debated, inflation is widely accepted by physicists. However, a consequence of this theory is that there must be other parts of the Universe that are still accelerating. However, due to the quantum fluctuations of space-time, some parts of the Universe never actually reach the end state of inflation. This means that the Universe is, at least according to our current understanding, eternally inflating. Some parts can therefore end up becoming other universes, which could become other universes etc. This mechanism generates an infinite number of universes.
By combining this scenario with string theory, there is a possibility that each of these universes possesses a different compactification of the extra dimensions and hence has different physical laws.The cosmic microwave background. Scoured for gravitational waves and signs of collisions with other universes. NASA / WMAP Science Team/wikimedia
The universes predicted by string theory and inflation live in the same physical space (unlike the many universes of quantum mechanics which live in a mathematical space), they can overlap or collide. Indeed, they inevitably must collide, leaving possible signatures in the cosmic sky which we can try to search for.
The exact details of the signatures depend intimately on the models - ranging from cold or hot spots in the cosmic microwave background to anomalous voids in the distribution of galaxies. Nevertheless, since collisions with other universes must occur in a particular direction, a general expectation is that any signatures will break the uniformity of our observable Universe.
These signatures are actively being pursued by scientists. Some are looking for it directly through imprints in the cosmic microwave background, the afterglow of the Big Bang. However, no such signatures are yet to be seen. Others are looking for indirect support such as gravitational waves, which are ripples in space-time as massive objects pass through. Such waves could directly prove the existence of inflation, which ultimately strengthens the support for the multiverse theory.
Whether we will ever be able to prove their existence is hard to predict. But given the massive implications of such a finding it should definitely be worth the search.
Eugene Lim, Lecturer in theoretical particle physics & cosmology, King's College London
This article was originally published by The Conversation. Read the original article and read other articles from their cosmology series here.
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There might just be something worse than what you mention. -
I’m having enough of a struggle just coping with this obvious universe for now; much less multiple situations. - Twinkie needs a vacation! Simplify! Simplify!
Where Moochelle is the beard.
Just keep the sports almanac away from Biff and all will be well.
That’s where Liberals live.
I saw this already in a movie called “The Mist” (Stephan King book). The scientists’ window into the other dimension was actually a door and the things coming through were hungry and not at all house broken.
Must be yet another variation... Sulu liked women in that universe.
“It was dreamed up solely to provide some response to the unmistakable theistic implications of the anthropic principle and the beginning of the universe itself.”
Yep. The supposedly objective scientists are not at all objective when it comes to those implications. This is similar to one of the reasons Darwin’s writings became popular. The most exciting thing about the Theory of Evolution to many 19th century scientists was how it laid the foundation for atheism based on science.
for crying out loud- all you need is some chewing gum, bailing wire, duct tape, and a parallel universe tester kit which is available online at Ebay- The repair items are for the testers, as they no doubt will be used items in need of repair- but whatever-
I thought everyone had a parallel universe tester?
What happens if you connect your parallel universes in series? If one goes out do they all go out?
Touche’
Hugh Everett was the first to wonder at this back in 1957. The simple example was why do we see just one outcome of an experiment when many are possible?
When light passes through a polarizer so that it would be projected either vertically or horizontally, we only see one outcome. Basically, Everett’s hypothesis was that both states actually take place, but that they are at that instant separated from each other, and there can be no awareness of one to the other.
It’s sort of intriguing, to me at least, to think about what course our lives have taken, bifurcating endlessly through eternity.
God could eventually make a lot come out right in such a scenario. ...If that’s how He actually does it....
I would advise them to eat some mushrooms and see
what they think about that.
not if you have a series of failsafe emergency jumpers in place-
(you’ll find that info on page four of the instruction manuals)
ping
I’ve been living in an upside down world for the past 7-8 years. If someone can right it, go for it.
and series.
sort of - but women liking him not so much
There have been days when I have heard things on the “news” that made me think I had awakened in a “parallel universe….”
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Me too!
Maybe we are slipping back and forth between dimensions.
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